Time is almost always going to be a factor for students - so work strategically -
Don't waste valuable time deviating from the assignment instructions
Practice drawings - This seems at odds with saving time, but working out the kinks and seeing improvements will be worth the few extra sketching minutes.
Don't be forced to repost because the drawing is formatted incorrectly or doesn't follow assignment parameters - do it right the first time by re-reading directions and carefully going through the announcements